By Chris Deziel
Updated Mar 24, 2022
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Water becomes a powerful conductor when it contains dissolved ions. Lightning striking water can deliver lethal currents, but pure, distilled water remains an insulator.
Every natural water source—whether a lake, stream, pool, or hot tub—contains dissolved minerals such as sodium chloride, magnesium sulfate, and trace metals. These compounds break apart into positively and negatively charged ions when dissolved. The resulting solution is an electrolyte, meaning it can carry an electric current. Pure water, by contrast, lacks these ions and behaves as an insulator.
When lightning strikes a body of water, the enormous voltage momentarily charges the entire surface with millions of volts. The ions align with the electric field, allowing the current to flow rapidly through the water. Even low‑voltage devices, like a hair dryer left plugged into a bathtub, can become deadly because the appliance keeps the current flowing until a circuit breaker trips. The same principle explains why electrolytes are vital for human physiology: they conduct the tiny currents necessary for nerve impulses and muscle contractions.
Distillation removes dissolved minerals, producing water that behaves like a strong insulator—its conductivity is comparable to glass or air in laboratory tests. However, a pool or bathtub filled with distilled water would still not stop lightning, as the air around the water is a poor barrier to a high‑voltage strike. Moreover, once body fluids, dust, or surface residues dissolve into the water, its ion concentration rises, quickly restoring conductivity. Thus, while distilled water can reduce the risk from low‑voltage appliances, it offers no protection against lightning.
Bottom line: Never swim or enter a water body during a thunderstorm, and avoid using electrical devices in wet environments. If you’re ever unsure, err on the side of caution and stay out of the water.
